Mechanical forces are integral to the functionality and behavior of biological systems, from the cellular to the molecular level. Acoustic force spectroscopy (AFS), an emerging field, seeks to explore these intricate dynamics. Traditional methods in AFS, particularly those using bulk acoustic wave (BAW) devices, still lack sample visibility and have a low throughput. These limitations hinder the amount and type of data that can be gathered in the study of cellular and molecular mechanics. This research project addresses the challenge of enhancing visibility and throughput in AFS by developing a novel BAW device. Here we show the fabrication and implementation of a glass transversal resonator by femtosecond laser ablation and a simple glass-glass bonding technique using polyethylene film and cyanoacrylate glue, which enables two-dimensional particle trapping. Compared to existing BAW setups in AFS, our approach offers improved sample visibility and is capable of positioning particles at arbitrary locations between half- and full-wave mode equilibria by rapid mode-switching. It shows that the position can be predicted using a straightforward method to determine the stiffness of each mode. This advancement of acoustic force spectroscopy could pave the way for new approaches in biomedical research. For example, the ability to alter the force field in a predictable manner allows to form both force- and distance-clamps. More functional BAW devices could thereby not only enhance our understanding of cellular processes but also find broader application in fields like tissue engineering and medical diagnostics.

The use of optical fibres as distributed vision sensor within a contactless handling system is discussed in this study. The three primary light colours and a volume diffuser will be used to detect the edge of an object levitating on an air-bearing table. One building block of a bigger system is used that consists of one receiving fibre in the centre surrounded by three transmitting fibres, with each transmitting one primary light colour. Various experiments were executed to find a range where the object edge can be detected. The transition range for horizontal and vertical movement is found. The backscattering of light within the volume diffuser turned out to be much larger than thought. This backscattering causes a small light intensity range. Also, some disruptions in the emitted light caused no logical transition ranges. A model is made to see what happens to the transition ranges when the disruptions are eliminated. The red transmitting fibre is investigated to see the individual contribution to the light intensity received in the receiving fibre. The transition range got from that measurement is translated into the transition range for the green and blue transmitting fibres. Through interpolating the ranges, a total measurement range is found where the object edge can be detected at whatever angle the object is positioned. A bigger system can be made by connecting more building blocks. The proposal for future research is to investigate the positive or negative effects of connecting multiple building blocks.

Electret transducers utilize the electric field generated by an electret, a dielectric with a quasi-permanent embedded charge, to induce charge on an electrode. When the electret is moved relative to the electrode, the induced charge magnitude on the electrode changes, generating a current that can be used to convert mechanical energy into electrical energy. Micro-electret transducers are promising alternatives to conventional electromagnetic transducers for small-scale energy harvesting as they can achieve a high voltage output at low frequencies, can be miniaturized effectively, and can be manufactured using microfabrication methods. One-dimensional electrostatic models have been developed to predict the power output of electret transducers. However, for micro-electret transducers, fringing fields play a large role in the electrostatic domain. To be able to more accurately predict the output characteristics of micro-electret transducers, a two-dimensional (2D) electrostatic model is proposed. To verify the 2D model, a novel micro-electret transducer is designed. The novel electret design allows the micro-electret transducer to embed charges of only one polarity, increasing the power output of the electret transducer. The novel 2D model more accurately predicts the power output characteristics of the micro-electret transducer with the voltage output deviating 57%, compared with 317% by the conventional model predictions. Furthermore, the novel unipolar micro-electret transducer achieves double the power output and better charge stability compared with conventional electret transducers.

A pacemaker runs on a conventional battery that lasts for approximately 6-12 years, after which the pacemaker must be replaced. Converting the heart wall vibrations into electricity through a vibration energy harvester has been considered a promising solution to this problem. However, the complexity of the heart signals on which the energy harvester has to operate is a challenge. The human heart signal is a broadband signal, consisting of a varying acceleration amplitude at low frequencies. Most of the testing signals used in the labs are harmonic signals, Gaussian white noise or Gaussian coloured noise. These signals do not have the same characteristics as a human heart signal. In addition, the dynamical behaviour of an energy harvester differs per input signal. Therefore, it is important to test energy harvesters on the operation signal, in this case human heart acceleration signals. A heart signal differs per person depending on, for instance, someone's age, sex and health. This means that multiple human heart input signals are needed. Ethical requirements make the measurement of these signals with the necessary details a challenge in itself. In order to meet this demand and to avoid this ethical issue, a heart signal generator is developed as a first step towards the testing of energy harvesters on an approximation of human heart signals. Three different sources of heart signals are combined in order to obtain a new source of heart signals, an approximation of reality, which can be used for the testing. Speckle Tracking Echocardiography signals, open-chest pig heart acceleration signals and human chest motion acceleration signals are analysed and their characteristics are used as the source for the heart signal generator. This heart signal generator is able to mimic multiple heartbeats and the influence of the heart rate on the amplitude and signal duration. The disadvantages of accelerometer measurements are compensated with the advantages of Speckle Tracking Echocardiography measurements, and vice versa, in order to obtain an accurate and detailed heart signal. The output of the heart signal generator is a one-dimensional acceleration signal. An energy harvester is tested on multiple generated heart signals for a heart rate range of 120-200 bpm. It was observed that the mean power output and the efficiency of the energy harvester differs per heart signal. This shows that testing on multiple heart signals is crucial in order to validate that enough power is generated for charging the battery.

Graphene is considered a promising material due to its unique electrical characteristics and excellent mechanical properties. These extraordinary properties make graphene a suitable material for applications like mechanical reinforcements, protective coatings, supercapacitors, sensors, etc. However, when trying to extract these properties experimentally, the challenge of producing pristine graphene prohibits researchers from attaining the required results. The challenge is primarily due to the formation of structural or surface imperfections during the fabrication, transfer or manipulation of the membrane. In addition, graphene possesses a low bending rigidity which inevitably leads to the out-of-plane crumpling of the film. So, determining the effect of these imperfections on the mechanics of graphene is critical to ensure development in the research field and application pertaining to graphene. The main focal point of this work is to experimentally determine the effects of surface corrugations, in the form of out-of-plane crumples, on the mechanical constants of the graphene membrane. In this study, two types of graphene membranes are considered, one is a flat membrane, and the other is a heavily crumpled membrane. The atomic force microscope is used to probe the membranes, and the mechanical constants are extracted from the resulting force deflection characteristics. The mechanical constants of the flat membrane, 2D Young’s modulus (E2D) and pretension (σ0) were found to be 140.42 ± 44.52 N/m and 0.119 ± 0.049 N/m respectively. The values obtained suggest a softening behaviour of the membranes, which is due to the intrinsic crumpling of the membrane in the out-of-plane direction. Surprisingly, in the case of heavily crumpled membranes, E2D and σ0 were found to be 393.34 ± 145.12 N/m and 0.203 ± 0.069 N/m respectively. The values obtained suggests that the heavily crumpled membranes provide greater resistance to deflection than the flat samples. However, it is essential to understand that the values do not depict the effective Young’s modulus or intrinsic strength of the membrane. The presence of folds in the heavily crumpled membranes is the reason for their higher resistance to deflection. The evolution of these folds, when subjected to nanoindentation, is also discussed in this work. This research helps provide insights into how the graphene membrane responds mechanically in the presence of crumples and also provides progress in realising the applications of crumpled graphene membranes.

In this thesis, the analogy between the special theory of relativity and the dynamics of a laborer is developed in the context of labor economics. At the basis of this analogy stands an individual laborer who cannot supply more than 24$hours of labor in a day. This represents the theoretical limit to the flow of labor services (velocity). We argue this limit is analogous to the speed of light. The development of the analogy continues using hyperbolic functions independent of the demand frame of reference (frame of reference) and dependent on the degree of demand (rapidity) as well as the wage inelasticity (mass). This analogy describes the behavior of an individual laborer, detailing the quantity of labor services (position) and their flow, the wage (momentum) and the causation of changes in the flow of labor services (forces). These dynamics in labor economics are consistent with the theory of special relativity, demonstrating economic engineering principles. Economic engineering is applied to model an individual laborer using the newly developed analogy. The laborer's supply curve shows that wage inelasticity does not change when a laborer performs more labor. Instead, the nonlinear supply curve is attributed to the difference in a laborer's perception of time (proper time). The perception of time depends on the flow of labor services of the observer, making it possible to observe the labor market from different perspectives, including those of companies and laborers. The laborer's perspective on their supply is visualized on the Poincaré disk, from which occupational compositions and job transitions can be analyzed.

systems. Miniaturization creates challenges in handling delicate, small components, rendering traditional methods inadequate, necessitating an alternative. Acoustic levitation, which uses ultrasound waves to suspend objects without physical contact, offers a promising solution for containerless transportation. This technology can accommodate various materials regardless of their electromagnetic or optical properties and eliminates particle generation due to friction. Applications span across chemistry, biology, and high-tech industries, enabling manipulation and assembly of small components. However, acoustic levitation is highly sensitive to environmental factors such as temperature and air currents, which can compromise stability. Most studies have primarily focused on understanding the dynamics of acoustic levitation and developing models to describe the underlying physical phenomena. This study shifts towards actively controlling them by adding artificial damping. To achieve this, this thesis introduces the use of event cameras, which capture high-speed movements without redundant frame data, making them highly efficient. The goal is to create a control feedback loop to correct for disturbances and improve the step response of acoustically levitated objects. The methodology involved integrating an event camera into the acoustic levitation setup and implementing a tracking algorithm to track the position of a levitated object. System identification was performed, revealing higher-order harmonics and allowing the development of a second-order model of the levitated object. This model was used to design a feedback controller integrated with the event camera. Experimental results demonstrated a substantial improvement in system performance. The bandwidth of the system improved to 40.8 Hz, the settling time decreased from 10 seconds to 0.8 seconds, an improvement by a factor of 12.5. Additionally, the steady-state error was significantly reduced, and the introduction of artificial damping successfully eliminated the first resonance peak, though a second higher-order resonance peak remains. This work highlights the potential of using event cameras in control loops for acoustic levitation, representing a significant step towards more precise control of levitated objects.

Photonics biosensors convert biomolecular interactions into quantifiable optical signals for biomedical analysis, which enable continuous monitoring of health indicators. Among them the microring resonator has a good sensing performance and a very broad application prospect. This thesis studies sensing with microfluidic integrated microring resonator photonic microchips. This thesis adopts finite element method to simulate the optical behavior of waveguides and reactions in the microfluidic channel. The microfluidic channel was designed and prepared and then integrated to the photonic chip. The optical performance parameters of the micro ring resonator were tested by using a high-precision optical test system. The sensing performance of waveguide microring was studied using different aqueous solution as the detection object. The feasibility and effectiveness of the optical waveguide chip sensing have been preliminary verified.

In the semiconductor industry, the demand for a continuously higher throughput puts tough requirements on the force capacity and accuracy of actuators. Reluctance actuators, as a promising alternative to the present state-of-the-art Lorentz actuators, are capable of achieving much higher force densities. On the other hand, reluctance actuators suffer from strong intrinsic nonlinearity, such as the quadratic and position-dependent current-force relation, negative stiffness, and magnetic hysteresis, making accurate control challenging. These nonlinear effects can be much suppressed if, instead of controlling the current through the driving coil, the magnetic flux in the actuator core is controlled. As a preparation step for implementing the flux control experimentally on reluctance actuators, this project aims to design and realise the necessary hardware for flux control implementation, including a reluctance actuator prototype and a test setup, and then dynamically calibrate the actuator for flux measurement and control. More specifically, a hybrid reluctance actuator prototype that is suitable for flux control, as well as a test setup for measuring the position and dynamic force output of the actuator, are designed and realised. Using this setup, relations between key variables of the actuator are measured to enable nonlinear compensation in the current and flux control, and a hybrid flux measuring scheme using a Hall sensor and a sense coil is proposed and experimentally implemented. Although noise in the flux measurement is effectively minimised, the result shows a mismatch in the frequency domain between the outputs of the Hall sensor and the sense coil, where further investigation is needed to improve the feasibility of this approach. Furthermore, a hybrid force measuring scheme is proposed and implemented where errors of the load cell due to high-frequency dynamics of the setup can be compensated using acceleration measurements, leading to a wider frequency range for the force measurement. With the realised hardware and the obtained measurements from this project, the next step in future works would be to experimentally implement the flux control on a reluctance actuator and compare its performance with the standard current control.

Surface corrugations in graphene negatively effect the unique and useful properties of graphene. In order to exploit the special properties of graphene, it is therefore important to understand the phenomenon of wrinkling. In this study, strain engineering was applied to study the flattening of wrinkles in a suspended graphene membrane. Initially, a MEMS device was used for inducing strain in a suspended membrane. Transfer of graphene onto the MEMS device was challenging and in this study not successful. Suspended graphene drums with an electrostatic backgate were used as an alternative system for strain engineering. A stress-strain curve was calculated from the drum deflection measurements as a function of backgate voltage. The stress-strain curve exhibits a non-linear regime that is due to wrinkle flattening and a linear regime that is due to membrane stretching. The Young’s modulus of the membrane is determined using three different methods. An analytical model for the stress-strain curve of a wrinkled membrane proposed in [1] is fitted to the experimental data. The good agreement between the model and the data validates the model and provides insight into the parameters that govern the behavior of the membrane. Wrinkles were visualized individually and were clearly decreasing in size with increasing backgate voltage. Also the surface correlation length was shown to increase with backgate voltage, indicating flattening of wrinkles.

Nanomechanical resonators made of two-dimensional (2D) materials are the subject of intensive research due to their remarkable properties, allowing them to operate at high frequencies with high sensitivity. However, dissipation losses and manufacturing issues have prevented them from reaching their full potential. This thesis aims to overcome these challenges by dry-transferring 2D materials onto a MEMS and clamping them using electron beam-induced deposition. By in-plane straining the membranes using MEMS, the tensile energy is increased, thereby diluting intrinsic losses. This approach increased the Q-factor of 2D material resonators by 91% and allowed measuring forces down to sub-piconewtons, outperforming commercially available silicon-based force sensors.

Two-dimensional (membrane) materials have been receiving much scientific attention due to their unique material properties that can be used to study the smallest physical phenomena. One such material is graphene, perceived as the holy grail in material physics, due to its unique material properties. Its aspect ratio diminishes the bending rigidity and allows wrinkles, ripples and other morphological imperfections to dominate the mechanical behaviour. Applying tension is a necessity to control these geometrical imperfections and simultaneously opens up pathways to study physical phenomena such as magnetism, superconductivity, optics and much more. Typically, this tension is applied using electrostatic forces, which alters amongst others, the electric properties of the material. Mechanically applied tension offers a solution to this problem but comes at the cost of difficult manufacturability. In this work, a new method to incorporate 2D materials with N/MEMS is presented. The dynamics of mechanically tensioned graphene are probed in linear and nonlinear regimes. The former regime finds the exact opposite of what is observed in electrostatically tensioned membranes. The latter shows exotic nonlinear effects that can be tuned by applying tension. Furthermore, it is identified that the dynamics of the MEMS device are coupled to that of the resonating membrane despite their mass and stiffness being roughly five orders of magnitude apart. The bottleneck of this project is the adhesion force between the two is insufficiently strong to apply significant strain allowing slippage to occur.

This thesis explores the challenges of using ultrathin graphene membranes in microelectronic mechanical sensors (MEMS) technology, specifically in the development of MEMS microphones. Graphene, being only an atom thin and one of the strongest known materials, offers promising potential for further miniaturization of MEMS microphones. However, the mass loading effect on the graphene membrane can impact the device’s resonance frequency and bandwidth.To address this issue, this study analyzes the dynamic response of the graphene membrane under different pressures and membrane parameters, such as diameter and thickness. The membranes are fabricated by using chemical vapour deposition, after which the membranes are transferred over a cavity. The measuring setup uses a laser Doppler vibrometer to measure the deflection of the membranes and investigate their dynamic response. Pressure-dependent experiments are performed to measure the resonance frequency of the membrane’s response, and the relationship between the radius, thickness, and resonance frequency is explored. By doing these measurements we explore the effect of air loading to investigate the ultimate performance limits of graphene membranes for microphone application. The experimental results show a clear presence of the air loading effect and align with earlier models of the resonance frequency with mass loading effects. The thesis validates the accuracy and reliability of the measurements and contributes to the body of knowledge surrounding the topic. The limitations of the study include fabrication imperfections and setup difficulties like a limited bandwidth of the piezo-shaker used for the actuation of the membranes. The assumptions made about limited cavity effects are also discussed. Future research could explore the impact of an added backplate with venting holes for capacitive readout. Next to that, the influence of air loading on the system’s damping could be researched.

Acoustic levitation is an novel method that could lend itself very useful to fast and precise transportation of small objects. To verify the acoustic field and the modelling assumptions, the acoustic field must be visualised and quantified. Different methods to visualise a pressure gradient are investigated and rated against design requirements. These requirements are: 1. difficulty, as the setup should be buildable within the period of a MSc. thesis. 2. Time per measurement and 3. measurement sensitivity. It is decided that using a double coincidence spherical mirror schlieren setup is most suitable measurement method. To capture the high speed sphenomena of ultrasound acoustic waves in air, the schlieren light source is pulsed and matched to the frequency of the acoustics to ’freeze’ the acoustic wave in the air. Parameters that influence the schlieren image are identified and studied. These parameters are duty cycle, cut-off, ISO, light source phase delay and light source frequency. A horizontal cut-off is determined as the best, while it is determined that the other parameters can be adjusted dependent on the acoustic field. The acoustic field generated by double phased array is observed. Trap locations and types can be identified using the schlieren system. Quantification of the schlieren images has been attempted but without satisfactory results, mainly due to an interesting observation regarding a correlation between the camera focus distance and the pressure gradient. The schlieren system is a useful research tool and successful at visualising the pressure gradient under the assumption that it is constant over the optical axis. Further research is needed to for quantification and to assess the impact of the observation.

From the research in the field of mechanobiology, it is evident that cells exert different force magnitudes while growing based on the biomaterial these are in contact with. The magnitude of the exerted force determines certain behaviors and mechansims of the cells, such as differentiation. For this reason, it is proposed to develop a distributed force sensor using a photonic integrated circuit with a PDMS top layer to measure the exerted forces, which can be used to study the behavior of the cells. Unlike conventional measurement techniques, this method allows cell exerted distributed forces at µN levels to be detected and monitored over a continuous time-span of multiple days and weeks. The photonic integrated circuit design consists of a sensing array of silicon photonic ring resonators for force sensing. On each sensor row, reference ring resonators are applied as well to cancel out the spectral noise caused by temperature drifts and laser wavelength repeatabilities. The reference ring resonators are shielded against cell exerted forces with a commercial hybrid-polymer, which has a Young's modulus of around 1 GPa. Using the reference ring resonators resulted in a theoretical measurement resolution of potentially as small as approximately 0.012 pm. Finally, the force limit-of-detection of the designed distributed force sensor remains below 1 µN when the force exertion area does not exceed 100 µm2 and assuming a sensitivity of 65.41 nm/RIU for one of the multiplexed ring resonators.

Within this research a nouvelle microphone design is posed, modelled and tested. The design consists of a cavity covered by a membrane and having a venting channel, it uses the squeeze-film effect in order to link pressure to the membranes resonance and by extension acoustics to the membranes resonance. In [1] the squeeze-film effect was first used in order to measure static pressures, an idea on which this research builds in order to use it to measure acoustic pressures and so create a new type of microphone. The aim of this research is attaining a proof of concept and a preferably also model capable of accurately depicting the functionality of new designs. Proof of concept is given, as the first ever squeeze-film microphone is shown to functionally measure an acoustic chirp. Whether, the model created for and given in this research is truly capable of predicting a new designs functionality is as of yet unproven. [1] R. Dolleman, Dynamics of interacting graphene membranes. PhD thesis, Technische universiteit Delft, 2018.

Micro-ring resonators based on silicon-on-insulator (SOI) waveguide are widely used as sensors due to their small size and high sensitivities. After being fabricated on an integrated photonic technology, it can be applied in bio-chemical analyses crucial for human health monitoring, disease diagnoses, etc. In this project, we develop and construct a robust experimental setup based on the SOI based micro-ring resonator, which combines temperature control and modification of the waveguide cladding via surface treatments and microfluidic integration. The setup gives a controlled environment for characterizing the photonic chip under various chemical treatments or different physical ambient. After the setup is built, several experiments were performed to test the optical characteristics of the ring resonator, under different scenarios. These include temperature control, treatment of chip surface with sodium chloride and glucose solutions at varying concentrations, and lastly chip-surface functionalization for biomarker detection. With these experiments (also validated by numerical simulations), we demonstrate the robustness and reliability of our setup.

Dynamic Atomic Force Microscopy (dAFM) is an extremely powerful tool for exploring surface topology and nanoscale manipulation and characterization. A feature of dAFM is the existence of highly nonlinear forces between a cantilever tip and sample. One of these forces that plays a large role in operation of AFM is the van der Waals (vdW) force. This force is characterized in part by the Hamaker constant H and cantilever tip radius R. Measuring these two properties quickly and accurately can facilitate further characterization methods in dAFM. This research will focus on creating methods in which H and R can be extracted using the dynamic response of a cantilever. The vdW force was used to extract H by analyzing the softening behavior of Frequency Response Curves (FRCs). Electrostatic forces were used to extract R by applying a simplified Kelvin Probe Force Microscopy (KPFM) technique. The method to extract H was demonstrated numerically, and the method to extract R was proven experimentally and validated using a Scanning Electron Microscopy (SEM) image.